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AR# 31762

Description

In the XST report, I see a mismatch in the Device utilization summary register count and the Partition Resource Summary Register count. Why do I see this, and which count is correct?

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Partition Resource Summary:

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Partition "/ff_top":

Number of Slice Registers: 319

Number of Slice LUTs: 300

Number of BUFG: 3

Number of bonded IOBs: 84

Partition "/ff_top/host_if_unit_inst":

Number of Slice Registers: 154

Number of Slice LUTs: 264

Partition "/ff_top/se_unit_inst":

Number of Slice Registers: 5144

Number of Slice LUTs: 11972

Partition "/ff_top/dpi_unit_inst/ff_swap1_inst":

Number of Slice Registers: 24

Number of Slice LUTs: 37

Partition "/ff_top/dpi_unit_inst":

Number of Slice Registers: 210

Number of Slice LUTs: 295

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Device utilization summary:

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Selected Device : 4vlx25ff668-10

Number of Slices: 6898 out of 10752 64%

Number of Slice Flip Flops: 5835 out of 21504 27%

Number of 4 input LUTs: 12868 out of 21504 59%

Number of IOs: 84

Number of bonded IOBs: 84 out of 448 18%

IOB Flip Flops: 16

Number of GCLKs: 3 out of 32 9%

Solution

The problem is that the Partition Resource Summary rolls the IOB Flip-Flop counts into the Slice Flip-Flop numbers, while the Device utilization summary breaks out the IOB Flip-Flop number from the Slice Flip-Flop number.

Both numbers are correct; however, the Partition Resource Summary contains IOB Flip-Flops in the counts.

To be consistent, we are planning on fixing this in the next major release of the design tools.